This F32 training proposal seeks support for a three-year program of research and training to be carried out at the University of Chicago and NORC under the guidance of Dr. Linda Waite. This research seeks to assess the role of physical health in the development of mild cognitive impairment and dementia. A second goal is to advance our understanding of the disability that results from dementia by examining social and psychosocial factors that reduce the likelihood of cognitive decline. Its specific aims are (1) To examine the extent to which behavioral factors (alcohol consumption, obesity, physical activity) and health conditions act as predictors for cognitive impairment in older adults using longitudinal, population-based data, (2) To develop a broad definition of mild cognitive impairment (MCI) usable in non-clinical settings, and (3) To examine the extent to which incidence, and changes in, cognitive functioning are associated with psychological factors (depression, hopelessness) and social factors (social network participation or integration, social support). This work will expand the field of demography of aging in several ways, by: (1) examining factors that might alter the life course at the onset of cognitive decline; (b) developing new methods to identify cognitive decline in older adults earlier than in clinical settings; and (c) extending social support theory by applying it to diseases of senescence care. Analysis of data will come from two sources: the population-based Health and Retirement Study (HIRS) and microfindings from interviews with a small, non-random sample of individuals who experience dementia-associated disability.